This application claims benefit of Japanese Application No. Hei 11-200730 filed in Japan on Jul. 14, 1999, the contents of which are incorporated by this reference.
1. Field of the Invention
The present invention relates to a multiple-point automatic focusing camera which detects a focal point in plurality of focal point detecting regions.
2. Description of the Related Art
Since before, a multiple-point automatic focusing camera which detects a focal point in plurality of focal point detecting regions has been well known. In such a multiple-point automatic focusing camera, generally, the focal point is detected with three points which include the center of a screen and two points, right and left to the center. Alternatively, the focal point is detected with five points including the above three points plus two points, above and below the center. Recently, cameras which detect the focal point with more distance measuring points or in more focal point detecting regions have been marketed, so that the number of the distance measuring points is inclined to increase.
Further, there is a prospect that the distance measuring points will be disposed substantially in an entire range of an shot area in future. With such an increase of the distance measuring points in a surrounding region of the image screen, an irradiation range of a supplemental light is inclined to be expanded. The supplemental light mentioned in this specification means a light which is to be irradiated to an object to increase light intensity of an object image if the light intensity of the object image is not enough when the focal point is detected.
As a light source of the supplemental light or a supplemental light source, for example, a light emission device such as light emission diode(LED) is used and designed specially to coincide with automatic focusing function of a camera. This light emission device is classified into a type incorporated in the camera and a type installed on an external attachment stroboscope. The external attachment stroboscope is used widely for multiple kinds of cameras from a widely marketed camera to a high grade professional camera. Therefore, the supplemental light source provided on the external attachment stroboscope is not always designed specially to correspond to the automatic focusing function of a camera to which the external attachment stroboscope is to be attached. Therefore, depending on the distance measurable range of the camera, a supplemental light is not distributed to distance measuring points in the periphery of the shot screen within an irradiation range of the supplemental light of the external attachment stroboscope, so that when luminance of an object is short, the focal point cannot be detected at the distance measuring point in the periphery of the shot screen.
Thus, use of the external attachment stroboscope corresponding to the distance measuring range of the camera is demanded. However, because the distance measuring range of the camera is inclined to expand as described above, if an external attachment stroboscope equipped with a supplemental light source corresponding to the distance measuring range is required each time when a new camera having such an expanded distance measuring range is introduced, economic burden of user increases. Further, development of such a supplemental light source needs countermeasure against increases of production cost and unit size accompanied by an increase of the irradiation range. Securing an irradiation range corresponding to the distance measuring range of a camera is an important problem for the supplemental light source.
Under the above described background, following conventional technologies are already known about the supplemental light source for use in the multiple-point automatic focusing camera.
Japanese Patent Application Laid-Open No.SHO63-78133 has proposed a technology for coping with changes in position of the focal point detecting region by providing a supplemental light source having an irradiation range expanded up to the periphery around the focal point detecting region in the center of the screen.
Japanese Patent Application Laid-Open No.SHO63-78134 has proposed a technology for saving electric power by stopping the supplemental light when it is determined that the supplemental light does not reach the focal point detecting region in the periphery of the screen so as to stop waste irradiation of the supplemental light.
Japanese Patent Application Laid-Open No.SHO63-82407 has proposed a technology for saving electric power by providing with a supplemental light source capable of projecting the supplemental light to all the focal point detecting regions and then projecting the supplemental light to only a selected focal point detecting region.
Japanese Patent Application Laid-Open No.HEI3-220535 has proposed a technology for saving electric power by selecting a focal point detecting region which excludes irradiation of the supplemental light in order to avoid the irradiation of the supplemental light to a focal point detecting region in the periphery of the screen in which detection of the focal point is difficult.
Japanese Patent Application Laid-Open NO.HEI11-52225 has proposed a technology that two supplemental light sources are provided on both sides of a photographing lens and by selecting any supplemental light depending on the focal point detecting region, a supplemental light suitable for a camera posture and a position of the focal point detecting region is projected.
However, the Japanese Patent Application Laid-Open No.SHO63-78133 has such a problem that if the irradiation range of the supplemental light source is expanded, the sizes of the supplemental light source increase so that production cost also increases.
Further, the Japanese Patent Application Laid-Open No.SHO63-78134 has such a problem that a focal point detecting region not irradiated with the supplemental light is generated so that a focal point detecting region in which accurate focal point detection is difficult due to a shortage of luminance is generated.
Further, the Japanese Patent Application Laid-Open No.SHO63-82407 has such a problem that by providing with a supplemental light source for irradiating all focal point detecting regions, the size of the supplemental light source is increased thereby inducing an increase of production cost.
Further, the Japanese Patent Application Laid-Open No.HEI3-220535 has such a problem that a focal point detecting region not irradiated with the supplemental light is generated so that a focal point detecting region in which accurate focal point detection is difficult due to shortage of luminance is generated.
Further, the Japanese Patent Application Laid-Open No.HEI11-52225 has such a problem that by providing with two supplemental light sources, a supplemental light source loading space increases and production cost also increases.
Accordingly, a first object of the present invention is to provide a multiple-point automatic focusing camera capable of detecting the focal point in any focal point detecting region even at the time of a low luminance while suppressing the size of the supplemental light source.
Then, a second object of the present invention is to provide a multiple-point automatic focusing camera having an advantage of a stroboscope light source capable of securing a wide light distribution angle and an advantage of the LED capable of reducing dazzling and securing a high focal point detecting accuracy with a low power consumption by using the stroboscope light source and LED depending on the focal point detecting region.
To achieve the above object, the present invention provides a multiple-point automatic focusing camera for detecting the focal points in plurality of focal point detecting regions, comprising: a light emission means for emitting a flash light to an object; and a supplemental light control means for controlling the light emission means as a supplemental light source. Then, if it is determined that the supplemental light is necessary for detecting the focal point, and the focal point is detected at least in a focal point detecting region located in the periphery of a shot screen, of the plurality of focal point detecting regions, the supplemental light control means is activated.
This objects and advantages of the present invention will become further apparent from the following detailed explanation.